If he is sidelined, it would be a blow for Premier League champions Liverpool, who were deprived of Senegal global forward Sadio Mane earlier in the season when he too tested positve for coronavirus, although he has since returned to the team.
According to a Goal.com report, footage has emerged showing Salah celebrating at his brother's wedding in Cairo earlier this week, with no social distancing or protection such as face masks in place.
With his penalty against Manchester City before the worldwide break, Salah moved level with Fernando Torres (in 2009-10) and Robbie Fowler (1995-96) for the most goals through eight games of a Premier League campaign for Liverpool.
Medical swabs on the national team "showed that our global player, Mohamed Salah, Liverpool star, was infected with the coronavirus", it said in a tweet, adding he was "not suffering from any symptoms".
Later, a statement tweeted by the Egyptian Football Association said another round of tests will be taken by three players from the Egyptian and the Togo teams who had tested positive in the first round.
Modi's alliance retains key India state Bihar after close poll fight
HAM president Jitan Ram Manjhi defeated former state Assembly speaker Uday Narayan Chaudhary in Imamganj of Gaya district. State Assembly speaker Vijay Kumar Chaudhary of the JD (U) was among the victors.
The EFA said Salah was now isolating, and that he would be "subject to more checks in the coming hours". Despite this development, the 28-year-old is not expected to be sidelined for long unless he develops mild symptoms of the coronavirus.
Egypt now sit third in Group G with two points from two matches.
Liverpool are not due to play again until their home Premier League match against Leicester on November 21.
Virgil Van Dijk has suffered a long-term knee injury while Fabinho is also sidelined.